The present disclosure relates generally to oilfield operations. More specifically, the present disclosure relates to techniques for sealing a wellbore.
Oilfield operations are typically performed to locate and gather valuable downhole fluids. Oil rigs are positioned at wellsites and downhole tools, such as drilling tools, are deployed into the ground to reach subsurface reservoirs. Once the downhole tools form a wellbore to reach a desired reservoir, casings may be cemented into place within the wellbore, and the wellbore completed to initiate production of fluids from the reservoir. Tubing or pipes are typically positioned in the wellbore to enable the passage of subsurface fluids to the surface.
Leakage of subsurface fluids may pose a significant environmental threat if released from the wellbore. Equipment, such as blow out preventers (BOPs), are often positioned about the wellbore to form a seal about pipes and to prevent leakage of fluid as it is brought to the surface. BOPs may employ rams and/or ram blocks that seal the wellbore. Some examples of ram BOPs and/or ram blocks are provided in U.S. Pat. Nos. 4,647,002, 6,173,770, 5,025,708, 7,051,989, 5,575,452, 6,374,925, 20080265188, U.S. Pat. No. 5,735,502, U.S. Pat. No. 5,897,094, U.S. Pat. No. 7,234,530 and 2009/0056132. The BOPs may be provided with various devices to seal various portions of the BOP as described, for example, in U.S. Pat. Nos. 4,508,311, 5,975,484, 6,857,634 and 6,955,357. Despite the development of sealing techniques, there remains a need to provide advanced techniques for sealing wellbores.